while this is all true, Lincoln offered to enshrine slavery into the United States Constitution if the South remains part of the Union, and the South refused. the fundamental thing that caused the South to secede was the fact that they did not trust the North to respect the economies and autonomy of the Southern States, even amongst the southerners who did in fact want to abolish slavery (Robert E. Lee among them).

of course, when you look at reconstruction, they were absolutely right.